Image authenticity & Photoshop

The topic of verifying image authenticity, covered well in the NY Times article It May Look Authentic; Here’s How To Tell It Isn’t, continues to draw considerable attention. Photoshop of course gets pressed into duty on the falsification side, so Adobe staff have been fielding a number of press inquiries on this subject.
What may be less obvious is Adobe’s interest in the other side of the coin: image analysis & authentication. Last summer Dr. Hany Farid (mentioned in the Times article) spent his sabbatical from Dartmouth at Adobe, collaborating with the Advanced Technology Group on tools & techniques for detecting image manipulation. Photoshop is heavily used by a wide range of government & scientific bodies, aiding in everything from detecting forged checks (you’d be amazed what a few adjustment layers can reveal) to cleaning up satellite imagery to analyzing the Dead Sea Scrolls (more info on that soon). At the request of image retouchers who need to document their work, we added the Edit History Log, making it possible to store a textual log of edits done to an image (essential for reproducibility). Combined with the ability to embed raw files as Smart Objects, this feature makes it possible for a Photoshop document to contain essentially the negative, the print, and a printable record of edits performed.
For more on Dr. Farid’s research & tools, see his own site as well as this National Geographic article on detecting forged artwork. For more on Photoshop in scientific imaging, now details how scientific features have grown over the last few releases, alongside white papers on best practices.

0 thoughts on “Image authenticity & Photoshop

  1. One other useful trick is to
    1) Duplicate layer
    2) Run Surface Blur with a low tolerance and less than 8 radius (play with this)
    3) change the mode to difference.
    4) you might also want to add an adjustment layer (levels) to expand the contrast to show what the difference really is
    This should show any areas that the detail has been airbrushed or smudged in some way. It will also highlight the underlying JPEG pattern.

  2. Chris, thanks for this tip, but could you explain a bit in more detail how to do this? I tried it and when I changed the mode to difference the image went black. Are all of these steps supposed to be performed on the second top layer? And is step 4 part of the process you suggest or another separate tip? Thanks for any info you can provide.

  3. First, do the processing on the top layer (created in step #1).
    Second, it is imperative that you add an adjustment layer (levels) and really crank up the gain to see the difference.
    Now, this is the Absolute Difference, so it isn’t dark where the difference is negative and bright where it is positive (like a High Pass filter), but it should isolate the texture/detail from the image so you can see if there are any “irregularities.”

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